Update _toc.yml

Author: ebatty

_toc.yml

@@ -93,10 +93,10 @@ parts:
       - file: Week11/Video113.ipynb 
       - file: Week11/Week11Tutorial1.ipynb 
   #     - file: Week11/Week11Tutorial2.ipynb 
-  #   - file: Week12/Overview.md
-  #     sections:
-  #     - file: Week12/Video121.ipynb
-  #     - file: Week12/Video122.ipynb
-  #     - file: Week12/Video123.ipynb 
-  #     - file: Week12/Video124.ipynb 
+    - file: Week12/Overview.md
+      sections:
+      - file: Week12/Video121.ipynb
+      - file: Week12/Video122.ipynb
+      - file: Week12/Video123.ipynb 
+      - file: Week12/Video124.ipynb 
   #     - file: Week12/Week12Tutorial1.ipynb